AWWA JAW62303

The foundation for lead control in drinking water distribution systems is based on Pb(II) chemistry. In recent years, however, Pb(IV) oxides have been identified in distribution systems, suggesting that they may be important relative to predicting and controlling lead concentrations at the consumer's tap. Therefore, a better understanding of the chemistry of Pb(IV) can be valuable to water utility managers as they make treatment decisions. This research shows that the two Pb(IV) dioxide polymorphs plattnerite and scrutinyite can form in chlorinated water and that these solids are less soluble in general than Pb(II) minerals historically used for lead control strategies. These findings have implications for water suppliers considering switching to a different type of disinfectant or making other treatment changes that could affect redox potential. If Pb(IV) oxides are in their distribution systems, any changes in redox potential (e.g., switching disinfectant from free chlorine to chloramines) could possibly fully reduce those solids to more soluble Pb(II) forms, potentially resulting in elevated lead concentrations. Includes 45 references, table, figures.